Production of nitric acid.



uns en re -ire; lrrn- Fltltlhi FREIDRIK W. DE JAHN, OE NEW YORK, N. 'Y.,ASSIGNOR T0 GENERAL GHEMICAL COMPANY, OF NEW YORK, N. Y., A CORPORATIONOF NEW! YORK.

PRODUCTION OF NXTRIG ACID.

Specification of Letters Patent.

Patented Apr. its, 1 .2 12.

' Application filed May 2, 1910. Serial No. 558,831.

- county and State of New York have invented certain new and usefulImprovements in the Production of Nitric Acid, of which the following isa specification.

This invention relates to the production of. nitric acid from a nitrateand sulfuric acid.

Broadly speaking, it consists in bringing these two things togetherunder such CUIIdl' tions that a practically quantitative yield of strongnitric acid is obtained not accompanied by any, or yery little, or" thedecomposition products of nitric acid. A further advantage is theeconomy in actual operation thus achieved, since heating to a lowerdegree of temperature and for a shorter time than under-the old processis needed and the accompanying smaller rate of wear and tear of theapparatus.

This invention. consists more specifically in bringing a nitrate,forexample sodium itratc, and sulfuric acid together in a vacuum sti lof any suitable construction, provided with a stirring device andmaintaining vacuum and a stirring of the material in the still whileheating the contents of the still to suitable temperature, which liesbelow that which the sodium bisuli'ate so formed (known technically alsoas niter cake and hereinafter called niter cake) melts; this lattertemperature is approximately 384 F.:l96 (1.; 302 F. 150 C. is asuitabletemperature for the conduct of this operation, in accordance with this,my invention.

This invention is based upon the discovery made by me that thedecomposition of sodium nitrate and of calcium nitrate by means ofsulfuric acid is practically complete at a temperature below 384 F. if avacuum be maintained and if the mass be stirred during the heating. ,Inthe prior practice literature, and patents, it is generally stated thatin order to obtain such practically complete decomposition of sodiumnitrate by means of sulfuric acid, the temperature of the mass will haveto be raised above the melting point of the sodium bisulfate armed. Ihave found that even when a full.

.acuum (but without stirring) is used the mass must be heated to atemperature above its melting point to get complete decomposition of thesodium nitrate, and l have further found that if, when the vacuum isused, the mass be properly stirred, the tempera ture need not go as highas the melting point of the sodium bisulitate formed; in fact that withproper attention the temperature need not exceed 302 F.:150 0.; underthese latter conditions the sodium bisulfate formed is a tractablepowder, which is a desirable property, and is not a hard mass or a hardlumpy material as it is'under all the old processes and practices.

I illustrate the nature of this, my inven' tion, by means of thefollowing examples, but in so'doing I wish to be understood as notlimiting myself to the exact details there shown since these can bevaried and altered without departing -from the nature oi my invention. 7

Example I: I place in the still. three thousand (3000) lbsof sodiumnitrate, produce a partial vacuum, (say six inches mercury) therein bymeans of a vacuum pump; then I draw into the still three thousand twohundred and seventy (3270') lbs. of sulfuric acid, containing 98% H 89then I gradnitric acid so obtained is, practically speaking, free fromdecomposition products of nitric acid. I

The apparatus which I find preferable may be described as follows,reference being had to the accompanying drawing showing a verticalsection of the apparatus in whichi A. represents a closed vessel for themirture. This vessel is preferably surrounded by a jacket B into whichwater or steam. may be introduced through the pipe C for maintaining thetemperature of the vessel A at the desired point. A pipe B may beprovided for withdrawing the water or steam from the jacket B it beingunderstood that both of the pipes C and D are preferably controlled'bymeans of valves (3 and D re- 119 spectively. The vessel A is closedthrough the medium of a cover E in which is secured a stufiing box Fthrough which the shaft G extends. The said shaft G has its inner endjournaled in the bottom of the vessel A. Stirring arms H are secured tosaid shaft at intervals within the vessel A and stationary liafile barsH are located between the stirring arms for the purpose of. holding thematerial and also serve as additional bearings for the shaft G. A bevelgear I is fastened to the upper end of the shaft G and meshes with abevel pinion J carried by a shaft K, rotatably mounted in suitablestationary bearings and providedwith a belt pulley L to which power maybe applied in any convenient manner. provided with a charging aperture Mfor the reaction mixture, said aperture being normally closed by meansof a cover M. The said cover E is further provided with and-nletNcontrolled by a valve N, through which the sulfuric acid is introduced.

is an'outlet pipe for the nitric acidvapors, controlled by a valve 0 andconnected with a condenser P.

Q is a vacuum receiver for the nitric acid, connected with thecondensing c011 located in the condenser P the air being exhausted fromsaid receiver through a pipe R S is an outlet pipe controlled by a valveS. The vessel A, is provided with a suitable door A for cleaningpurposes.

. I have .further found that'iby substituting dred and fifty (150) lbs.of calcium nitrate containing, for example 76% true calcium nitrate(Ca(l\ O3) 0.7% of calcium oxid (CaO) and 24% of water (H O) to this Iadd eighty (80) lbs. of sulfuric acid-containing ninety-five (95) percent. of sulfuric acid (H 80 I now gradually raise the temperature ofthe still and its contents to two hundred and sewnty-five 27 5) degreesFahrenheit (:135 C.) as shown bygthe thermometer, having a low vacuum ofsix 6) inches of mercury at the start and I gradually raise this vacuumto twenty-eight (28) inches of mercury whenever. distillation slacken-smaintaining the temperature above given throughout the operationanduntil the distillation is completed. The resulting calcium sulfate is inpowder form. In this example also the salient features of this, myinvention; are contained, namely, a practically quantitative yield ofstrong The cover E is.

nitric acid not accompanie by any or very little of the decompositionproducts of nitric acid, a rarefied atmosphere and a temsion rarefiedatmosphere as referring to atmospheric pressures in the containers ofless than the normal.

I claim: I p 1. The process which consists in stirring a nitrate and anacid together in a rarefied atmosphere while heating the material to atemperature at which the nitric acid distils off which temperature isbelow that at which the niter cake formed will melt.

2. The process which consists in stirring a nitrate and an acid togetherin a rarefied atmosphere while heating the material to. a

temperature at which the nitric acid distils off and below 384 degreesFahrenheit.

3. The process which consists in stirring a mixture of sodium nitrateand sulfuric acid together in-a rarefied atmosphere while heating thematerials to a temperature below the melting point of the niter cakeformed and distilling off the nitric acid produced.

4;. The process which consists in stirring a mixture of sodium nitrateand sulfuric acid together in a rarefied atmosphere while heating thematerial to a temperature below the melting point of the niter cakeformed, distilling off the nitric acid so produced and obtaining theniter cake in pulverulent or friable condition. 1

5. The process which consists in stirring a mixture of sodium nitrateand sulfuric acid together in a rarefied atmosphere while driving ofi'the nitric acid so produced, condensing the same and passing the escapegases therefrom through an absorbing tower. 1 6. The process whichconsists in stirring a mixture of sodium nitrate and sulfuric acidtogether in a rarefied atmosphere while heat-- ing the materials .to atemperature below the meltin point of the niter cake formed, driving 0the nitric acid so produced, condensing the same, passing the escapegases therefrom through an absorbin tower and obtaining the niter cakein p vernlent or friable condition.

In testimony whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

'JOHN A. Knmnnnoiz,

G. V. Rasmussen

